The document discusses a project to design and prototype a diesel piston engine for a light helicopter demonstrator. The project aims to reduce fuel consumption and emissions from current turbine engines. It is a 39 month, 9.3 million euro collaboration between Austro Engine, TEOS Powertrain Engineering, MECACHROME, D2T, and IFP Energies nouvelles. The goals are to demonstrate a 30% reduction in CO2 emissions and fuel consumption while minimizing weight impacts. Technical challenges include vibration control and achieving high power-to-weight ratios with good reliability. The target is to reach technology readiness levels 5 and 6 to allow pre-flight and flight testing.